In existing GaN light emitting diode, the P-side current flows through the transparent conductive layer from the P-type electrode and injects to the P-type conductive layer and even the active layer. However, on the one hand, since the hole concentration of the P-type conductive layer is generally low (1016 cm−3-1017 cm−3) and the hole mobility is mostly below 10 cm2/Vs, it is difficult for current to be uniformly distributed in the P-type conductive layer, which may lead to current crowding and excessive heat and finally influence luminous efficiency. In addition, luminous intensity is high under the electrode due to high current density. However, the light emitted is easily shielded by the electrode or absorbed by material after reflection, resulting in light output power loss.
On the other hand, though electrical conductivity of the N-type conductive layer is not as strict as that of the P-type conductive layer, a satisfied luminous efficiency is available if uniformly-distributed current is injected into the active layer.